1. Field of the Invention
The present invention relates to a communication system, a network for qualification screening/setting, a communication device, as well as a network connection method, and a qualification screening tool program used therefor. In particular, the present invention relates to a method for preventing connection to a network by a communication device infected by a virus or a communication device used to attempt unauthorized access and the like.
2. Description of the Prior Art
The recent widespread availability of personal computers (hereinafter referred to as PCs) and the Internet has led to the rapid enhancement of the significance of networks as socio-economic and socio-productive infrastructures. Unfortunately, the growing importance of networks as socio-economic and socio-productive infrastructures has led to an increase in attacks to networks in such forms as intentional distribution of viruses and unauthorized access to networks.
While viruses were conventionally spread to PCs and the like by storage media or e-mail, or via malicious web pages or web pages that have been vandalized through unauthorized access, there has been a recent proliferation of network viruses that are spread by merely connecting to the Internet.
As a result, there have been reports of damages caused when, for instance, a network PC, which is carried outside of the network and becomes infected with a virus when connecting to the Internet, spreads the virus to the entire network upon returning and reconnecting to the network while oblivious of its infection.
In such circumstances, when establishing a network, for the purpose of protecting the network not only from foreign attacks but also from contamination within the network, a quarantine network or system has been proposed involving performing a check (hereinafter referred to as quarantine processing) on a PC and the like, brought into a network from the outside, by connecting the PC and the like to a quarantine network to determine possible virus infection and whether latest patches are attached to software such as an OS (operating system), and lifting restrictions on connection to the network when it is determined to be safe (for instance, refer to Patent Document 1 (Japanese Patent Laid-Open No. 2005-216253)).